The present invention relates to a device for the discharge of tiles from treatment and firing ovens, particularly ovens constituted by elongated processing chambers along which the tiles are caused to travel by supporting and advancing devices, especially rollers. An oven of such a type is described in copending application Ser. No. 835,013 filed on Sept. 20, 1977, now U.S. Pat. No. 4,154,576, to which reference is made herein purely for illustrative purposes but without intending to limit thereby the invention and its application to ovens as described and claimed in such application.
Further, the invention is particularly applicable to ovens having a plurality of superimposed channels, such as those described in the aforesaid application and in other applications, or possibly having channels set side-by-side or channels that are superimposed and set side-by-side. But since the tiles travel independently in each of such channels and must be independently discharged therefrom, the apparatus and the devices according to the invention will be described essentially by referring to a single channel and a single tile treatment and firing plane, it being clear that they may be repeated for any number of channels or planes or treatment or firing chambers.
The invention is particularly useful in connection with modern high speed ovens of the type described, i.e. ovens in which the linear speed of the tiles is not less than 1 meter and preferably from 1 to 1.5 meter per minute.
The Prior Art
Processes and apparatus for discharging workpieces from various processing apparatus, by means of conveyors, e.g. roller or belt conveyors, are known. Specifically, it is known, e.g. from U.S. Pat. No. 4,105,398, successively to accelerate workpieces issuing from a furnace for the purpose of aligning them longitudinally between two initially converging and subsequently parallel guides. The accelerations have then the purpose of longitudinally distancing workpieces which have travelled through the furnace more or less side-by-side and which otherwise could not become longitudinally aligned.
When a result opposite to that of U.S. Pat. No. 4,105,398 is to be achieved, namely the workpieces are not to be longitudinally spaced apart and aligned but it is wished to bunch them together, it is known, e.g. from U.S. Pat. No. 3,529,711, to employ a stop bar.
In the device described by said patent, the workpieces are conveyed by a belt, come up against a stop bar, are temporarily stopped thereby and bunched together, and only subsequently are accelerated by a second belt in their bunched-up disposition, to facilitate their transfer onto a further belt running at right angles to the preceding ones.
It is also known from British Specification 1,168,589 to provide, in an apparatus for delivering candy bars for wrapping, an accelerating belt and a stop bar so disposed that the bars are accelerated before coming into engagement with the stop bar, and not thereafter as in cited in U.S. Pat. No. 3,529,711. The acceleration, the degree of which is not specified in the British Specification, has the purpose of allowing sufficient time for the stop bar transversely to align the candy bars to form transverse rows bunching-up of the succesive rows. The aligned rows are picked up by a belt running at right angles to the preceding one, raised to a higher level, and converted to wrapping means.
Attempts to adopt the means described in the aforesaid patents for the discharge of tiles from firing ovens, particularly high speed ones, do not furnish acceptable results and indeed make the orderly discharge of the tiles impossible. The tiles are loaded into the oven in transversely aligned rows, successive rows being spaced longitudinally apart to an extent that is moderate enough not to lower the production and the efficiency of the oven. No matter how perfect the inner conveyors of the oven, the rows become somewhat disarranged as they travel along the oven, which is some tens of meters long. When they issue from the oven, perfect transverse alignment must be re-established without slowing down the operation and while absolutely avoiding any danger of bunching-up or of contact between travelling tiles and particularly between tiles belonging to successive rows. It is therefore obvious that neither the longitudinal alignment provided by U.S. Pat. No. 4,105,398, nor the bunching-up provided by U.S. Pat. No. 3,529,711, can be adopted. At first sight it would seem that the method of the British Specification would solve the problem, since it provides transverse alignment without bunching-up. Experience, however, has taught that in connection with firing ovens for tiles, and particularly high speed ones, such method does not work. It is found that the time required for all the tiles of one transverse row to come into engagement with a stop bar, is long enough to cause disorderly contact between tiles of successive rows, and hence the breakdown of all the operation downstream of the oven. If it is attempted to overcome this drawback by increasing the acceleration between the oven and the accelerating conveyor in order to increase the spacing between successive tile rows, it is found that the drawback, far from disappearing, becomes more severe, because the increased speed increases the misalignment of the tiles and therefore the time required for the stop bar to align them, to an extent that is greater than the extent by which the spacing between successive rows is increased. Furthermore, it is found that if the acceleration is excessive, or if increased speed is maintained for too long a period of time, the tiles tend to rotate and to become set at sharp angles to the direction of travel, and re-alignment becomes practically impossible. In modern high speed ovens, these problems are particularly severe and the process conditions particularly critical.